The application is directed to high efficiency visible range dichroic polarizer elements and to a method for making the polarizer material.
U.S. Pat. No. 4,166,871 discloses iodine-stained borated polyvinyl alcohol light polarizing elements in which zinc ions are incorporated. These light polarizing elements are highly efficient; they exhibit high absorbance across the visible spectrum when in the crossed position and good transmittance across the visible spectrum when arranged in the parallel position. However, as increasing demands are placed on the performance of such polarizer elements attempts to improve their properties continue to be made.
For example, when used in applications such as goggles worn to protect the wearer's eyes against flashblindness from exposure to sudden bursts of extremely bright visible radiation it is desirable that the polarizer elements have extinction properties which are as high as possible while at the same time providing a transmissive state which is as high as possible so as not to interfere with normal vision. Typically, however, the prior art polarizer elements exhibit a transmittance-extinction tradeoff. The most direct way to obtain higher extinction is to increase the concentration of the dichromophore. Unfortunately, as is well known to those skilled in the art, an increase in the dichromophore concentration unavoidably results in a lower photopic transmittance level.
The present invention is directed to visible range light polarizing elements which exhibit higher transmissivity for a given extinction level, i.e., elements which exhibit higher extinction without compromising on high transmissivity and to a method for making the polarizer material.